Indexer performance Improvement

[t83714]

Indexer Performance Improvement

At this moment, the indexer expects the registry API to search for all relevant events through aspect reference links and send over a list of updated datasets rather than raw events.

This might lay too much pressure on the registry API & database.

Instead, we should:

• Indexer listens to the raw events instead, and the registry will only send over raw events
• The indexer should combine the raw events (e.g. events for the same record in the same page only trigger one index action) and re-construct the required dataset data from the raw events.
• Allow webhook to specify desired event page size in config